Search Publications
Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements
Jefferies, Stuart M.; Vorontsov, Sergei V.
Improving the accuracy and resolution of helioseismic inversions calls for more accurate modeling of the observational p-mode power spectra from which the solar oscillation frequencies are traditionally measured. We present a new technique of calculating the response function (leakage matrix) for Doppler velocity measurements that is based largely…
Host Galaxies of High-Redshift Active Galactic Nuclei in the Great Observatories Origins Deep Surveys Fields
Akiyama, Masayuki
The star formation rates and the stellar masses of the host galaxies of active galactic nuclei (AGNs) at high redshifts are key to understanding the evolution of the relation between the mass of the spheroidal component of a galaxy and the mass of its central black hole (Mbulge-M• relation). We investigate the host galaxies o…
OH Rotational Lines as a Diagnostic of the Warm Neutral Gas in Galaxies
Cernicharo, José; Goicoechea, Javier R.; Martín-Pintado, Jesus
We present Infrared Space Observatory (ISO) observations of several OH, CH, and H2O rotational lines toward the bright infrared galaxies NGC 253 and NGC 1068. As found in the Galactic clouds in Sgr B2 and Orion, the extragalactic far-IR OH lines change from absorption to emission depending on the physical conditions and distribution of …
Detection of Absorption Features in the X-Ray Spectrum of the Narrow-Line Quasar PG 1404+226: Possible Evidence of Accretion Disk Winds
Rao, A. R.; Dewangan, G. C.; Dasgupta, Surajit +1 more
We present the results of an analysis of data from XMM-Newton and Chandra observations of the high-luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray spectrum, and we find rapid variability (a factor of 2 in about 5000 s). When the X-ray spectrum is fitted with a two-component model that includes a power-…
Optical Sources near the Bright X-Ray Source in NGC 1073
Kaaret, Philip
New HST observations show that the bright X-ray source in the face-on spiral galaxy NGC 1073 is located near a ring of recent star formation with an age of 8-16 Myr. This strengthens the association of X-ray sources in spiral galaxies emitting near or above the Eddington limit for a 20 Msolar black hole with recent star formation events…
Direct Evidence for a Polar Spot on SV Camelopardalis
Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R. +2 more
We have used spectrophotometric data from the Hubble Space Telescope (HST) to eclipse-map the primary component of the RS CVn binary SV Cam over nine HST orbits. We find from these observations and the Hipparcos parallax that the surface flux in the eclipsed low-latitude region of the primary is about 30% lower than that computed from a PHOENIX mo…
The Double-Peak Spectral Energy Density of Gamma-Ray Bursts and the True Identity of GRB 031203
Dar, Arnon; Dado, Shlomo
A double-peak spectral energy density of prompt γ-rays, similar to that observed in blazars, is expected in the cannonball (CB) model of gamma-ray bursts (GRBs) produced in supernova (SN) explosions. The first sub-MeV ordinary peak is formed by inverse Compton scattering (ICS) of the ambient SN light by the CBs' electrons, while the second peak at…
Clusters in the Luminous Giant H II Regions in M101
Johnson, Kelsey E.; Chu, You-Hua; Chen, C. -H. Rosie
We have obtained HST WFPC2 observations of three very luminous but morphologically different giant H II regions (GHRs) in M101, NGC 5461, NGC 5462, and NGC 5471, in order to study cluster formation in GHRs. Images obtained in the F547M and F675W bands are used to identify cluster candidates and for photometric measurements, and images in the F656N…
Cataclysmic and Close Binaries in Star Clusters. V. Erupting Dwarf Novae, Faint Blue Stars, X-Ray Sources, and the Classical Nova in the Core of M80
Zurek, David R.; Hinkley, Sasha; Shara, Michael M.
Large populations of cataclysmic variables (CVs) in globular clusters have long been predicted, but the number of absolutely certain cluster CVs known in globular clusters is still less than 10. HST and Chandra observers have recently found dozens of CV candidates in several populous globular clusters. Confirmation and characterization of these ca…
Density Structure of a Preeruption Coronal Flux Rope
Chen, J.; Krall, J.
A density model is developed for a coronal flux rope with a specified magnetic field configuration in the noninteracting limit, for which transverse pressure forces can be neglected and flows are rapid enough (>1 km s-1) to invalidate a hydrostatic solution. In the coronal portion of the flux rope, we find that the plasma density is …